Crew seating arrangement

Flight

More than 100 mandatory modifications to the orbiter Discovery were
completed before returning to flight. Major modifications include:Brake
Improvements - This included changes to eliminate mechanical and
thermally-induced brake damage, improve steering margin and reduce the effects
of tire damage or failure. Modifications for first flight are the thicker
stators, stiffened main landing gear axles, tire pressure monitoring and
anti-skid avionics.17-Inch Disconnect - A positive hold-open latch design
feature for the main propulsion system disconnect valves between the orbiter
and the external tank (ET) was developed to ensure that the valve remains open
during powered flight until nominal ET separation is initiated.Reaction
Control System Engines The
RCS engines provide on-orbit attitude control and have
been modified to turn off automatically in the event any combustion instability
were to cause chamber wall burnthrough.Thermal Protection System - The TPS
was improved in areas on the orbiter in the wing elevon cove region, nose
landing gear door, lower wing surface trailing edge and elevon leading
edge.Auxiliary Power Unit - An electrical interlock has been added to the
APU tank shutoff valves to preclude electrical
failures that could overheat the valves and cause decomposition of the fuel
(hydrazine).Orbital Maneuvering System - To prevent development of leaks as
a result of improper manufacturing processes, bellows in critical
OMS propellant line valves have been replaced.Crew
Escape System - A pyrotechnically jettisoned side hatch, crew parachutes and
survival gear and a curved telescoping pole to aid the crew in clearing the
wing, have been added to give a bail-out capability in the event of a problem
where runway landing is not possible. An egress slide has been added to
facilitate rapid post-landing egress from the vehicle under emergency
conditions.

This mission was the first flight of a space shuttle
after the Challenger disaster. The launch was delayed for 1 hour
and 38 minutes because of unseasonable and unusual light winds aloft, and to
replace fuses in the cooling systems of two crew members' flight suits.

The primary objective of
STS-26 was to deliver
NASA's second Tracking and Data Relay Satellite to
orbit. In addition several scientific experiments were carried out.

The
primary payload for the
STS-26 mission, a Tracking a Data Relay Satellite
(TDRS-C), was successfully deployed six hours after
Discovery reached the orbit.The Tracking and Data Relay Satellite (TDRS-C) was the third
TDRS advanced communications spacecraft to be launched
aboard the Space Shuttle.
TDRS-1 was launched during Challenger's maiden flight
in April 1983 (STS-6). The second,
TDRS-B, was lost during the
Challenger
accident of January 1986.TDRS-3 and its identical sister satellite supported up
to 23 user spacecraft simultaneously, providing two basic types of service -- a
multiple access service which can simultaneously relay data from as many as 19
low-data-rate user spacecraft, and a single access service which will provide
two high-data-rate communication relays from each satellite.Transfer to
geosynchronous orbit was provided by the solid propellant Boeing/U.S. Air Force
Inertial Upper Stage (IUS). Separation from the
IUS occurred approximately 13 hours after
launch.The TDRSS satellites are the largest, privately-owned
telecommunications spacecraft ever built, each weighing about 5,000 lbs. (2,267
kg) Each satellite spans more than 57 ft. (17.37 meters), measured across its
solar panels. The single-access antennas, fabricated of molybdenum and plated
with 14K gold, each measure 16 ft. (4.87 meters) in diameter and, when
deployed, span more than 42 ft. (12.80 meters) from tip to tip.The
satellite consists of two modules. The equipment module houses the subsystems
that operate the satellite. The telecommunications payload module has
electronic equipment for linking the user spacecraft with the ground terminal.
The
TDRS has 7 antennas and is the first designed to
handle communications through S, Ku and C frequency bands.The Inertial
Upper Stage (IUS) was used to place
NASA's Tracking and Data Relay Satellite (TDRS-C) into geosynchronous orbit during the
STS-26 Space Shuttle mission.The
STS-26 crew deployed the combined
IUS/TDRS-C payload approximately 6 hours after liftoff, at
a low-Earth orbit of 160 nautical miles (296.3 kilometers). Following
deployment, Discovery maneuvered to a position 36 nautical mi. (66.6
kilometers) behind and 16 nautical mi. (29.6 kilometers) above the
TDRS-C/IUS before the two-stage motor ignited about 60
minutes after deployment. Upper stage airborne support equipment, located in
the orbiter payload bay, positioned the combined
IUS/TDRS-C into its proper deployment attitude - an angle
of 58 degrees - and ejected it into low-Earth orbit. Deployment from the
orbiter was by a spring-ejection system.Following the deployment, the
orbiter moved away from the
IUS/TDRS-C to a safe distance. The
IUS first stage was fired about 1 hour after
deployment.After the first stage burn of 145 seconds, the solid fuel motor
was shut down. After coasting for about 5 hours, 15 minutes, the first stage
separated and the second stage motor ignited at 12 hours, 29 minutes after
launch to place the spacecraft in its desired orbit. Following a 103-second
burn, the second stage was shut down as the
IUS/TDRS-C reaches the predetermined, geosynchronous orbit
position.Thirteen hours, 7 minutes after liftoff, the second stage
separated from
TDRS-C and performed an anti-collision maneuver with
its onboard reaction control system.The
IUS is 17 ft. (5.18 meters) long, 9 ft. in (2.74
meters) diameter and weighs more than 32,000 lbs. (14,515 kg), including 27,000
lbs. (12,247 kg) of solid fuel propellant.The
IUS consists of an aft skirt, an aft stage containing
21,000 lbs. (9,525 kg) of solid propellant which generates 45,000 lbs. (20,411
kg) of thrust, an interstage, a forward stage containing 6,000 lbs. (2,721 kg)
of propellant generating 18,500 lbs. (8,391 kg) of thrust and an equipment
support section. The equipment support section contains the avionics which
provide guidance, navigation, telemetry, command and data management, reaction
control and electrical power.

3M Company scientists flew an
experiment on
STS-26 to produce organic thin films with ordered
crystalline structures and to study their optical, electrical and chemical
properties.They call the experiment the Physical Vapor Transport of
Organic Solids (PVTOS), a name derived from the method which is employed to
produce organic crystals - vapor transport.The PVTOS experiment consisted
of nine independent cells 12 inches (0.3 meter) long and 3 inches (0.07 meter)
in diameter. Each cell contained a test tube-like ampoule containing organic
material. During space flight, the organic material was vaporized. Migrating
through a buffer gas, the vaporized material formed a highly ordered thin film
on a flat surface. After the samples were returned to Earth, 3M scientists
studied the films produced in space.

Protein Crystal Growth (PCG)
experiments to be conducted during
STS-26 was expected to help advance a technology
attracting intense interest from major pharmaceutical houses, the biotech
industry and agrochemical companies.Knowing the precise structure of these
complex molecules provides the key to understanding their biological function
and could lead to methods of altering or controlling the function in ways that
may result in new drugs.It is through sophisticated analysis of a protein
in crystallized form that scientists are able to construct a model of the
molecular structure. The problem is that protein crystals grown on Earth are
often small and flawed. Protein crystal growth experiments flown on four
previous Space Shuttle missions already have shown promising evidence that
superior crystals can be obtained in the microgravity environment of space
flight.During the flight, 60 different crystal growth experiments,
including as many as ten distinct proteins, was attempted in an experiment
apparatus that fits into one of the Shuttle orbiter's middeck lockers.In
the Protein Crystal Growth experiment, two of the 11 proteins processed -
including an enzyme believed to be key to the replication of AIDS - did not
produce crystals suitable for analysis.

Using the same kind of invisible
light that remotely controls our home TV sets and VCRs, mission specialist
George Nelson was to conduct experimental voice communications with
his
STS-26 crewmates via infrared, rather than standard
radio frequency waves (VCU (Voice Control Unit)).Six small infrared
transmitters and receivers (three each) were attached by Velcro to Discovery's
walls: two each on the flight deck and one each on the middeck. The
transmitters and receivers are connected by cable to a base unit which also was
attached by Velcro to a middeck wall. George
Nelson plugged his standard lightweight headset into a
belt-mounted unit which transmitted his voice via infrared lightwaves through
the receivers to the base unit. There, the signal was relayed to other crew
members using the standard Orbiter audio distribution system. Communications
back to George
Nelson from the other astronauts was travelled by the reverse
path.One major objective of the experiment was to demonstrate the
feasibility of the secure transmission of information via infrared light.
Unlike radio frequency (RF) signals, infrared waves will not pass through the
orbiter's windows; thus, a secure voice environment would be created if
infrared waves were used as the sole means of communications within the
orbiter. Infrared waves also can carry data as well as voice (e.g., biomedical
information). Future infrared systems are expected to be smaller, lighter
weight and produce better voice quality than their RF counterparts.A clear
line-of-sight path was not required between transmitter and receiver to insure
voice transmission. Infrared light will reflect from most surfaces and
therefore, quality voice can be transmitted even after multiple bounces. As
George Nelson moved around the vehicle, another major objective was
to demonstrate a "flooded volume approach", that is, to see if the wall-mounted
transmitters/receivers will pick up and deliver infrared signals without the
need for him to precisely align his transmitter with a target
receiver.Initial problems almost sidelined the tests when the voice
templates that were created prior to liftoff were found to have less than 60%
recognition for one crew member and less than 40% recognition for another. This
problem was corrected by retraining the templates. It was retested and found to
be operational with a recognition success rate of over 96%. It was concluded
that weightless conditions caused a fundamental change in human speech, making
the templates created prior to liftoff virtually useless.

The
Automated Directional Solidification Furnace (ADSF) was a special space
furnace developed and managed by Marshall Space Flight Center. It was designed
to demonstrate the possibility of producing lighter, stronger and
better-performing magnetic composite materials in a microgravity
environment.Four furnace modules were included in the ADSF, each processing
a single sample. The samples being used during the
STS-26 mission are manganese and bismuth composites.
They were processed at a constant melting and resolidification speed of one
about a third of an inch an hour. The total process times were 10.5 hours per
sample.Material processed during the mission was compared with samples of
the same metallic alloys processed in laboratories on Earth, as well as from
previous Shuttle and sounding rocket flights. Thermal, X-ray, chemical,
structural and magnetic analysis was made following the flight to determine
differences in the various samples.The ADSF flight hardware was housed in
three separate containers connected by power and data cables. The four furnaces
were housed in one container; another container had the electronic assembly
which controls furnace operations and yet another houses the control switches,
status indicators and a system which records data produced during the operation
of the furnaces.There were some equipment problems with the Automated
Directional Solidification Furnace.

Blood samples from donors with such
medical conditions as heart disease, hypertension, diabetes and cancer flew in
an experiment called Aggregation of Red Blood Cells (ARC) developed by
Australia and managed by
MSFC.The experiment was designed to provide
information on the formation rate, structure and organization of red cell
clumps, as well as on the thickness of whole blood cell aggregates at high and
low flow rates. It shall help determine if microgravity can play a beneficial
role in new and existing clinical research and medical diagnostic tests.The
first ARC experiment flew aboard STS-51C in January 1985. The
STS-26 experiment differed from its predecessor only
in the samples tested. The experiment hardware was unchanged.The flight
hardware weighed about 165 lbs. and was installed in three middeck lockers in
the crew cabin. The experiment consisted of a blood pump and storage subsystem,
thermal control system, pressure transducer and an electronics equipment
package to provide automated control and data acquisition.The ARC
experiment used eight experiment blood samples maintained at about 40 degrees
F. Each flew one sample at a time, into a viscometer, two optically transparent
polished glass plates separated by a spacer of platinum
foil.

Isoelectric Focusing (IEF) was a type of electrophoresis
experiment which separates proteins in an electric field according to their
surface electrical charge.The isoelectric focusing technique applied an
electric field to a column of conducting liquid containing certain molecules
which created a pH gradient in the column (alkalinity at one end, acidity at
the other end). This pH gradient caused the biological sample to move to a
location in the column where it has a zero charge - its isoelectric
point.The 65-pound experiment consisted of eight glass columns containing
protein, hemoglobin and albumen, with solutions which form the pH gradient
column of conducting liquid.The columns were arranged in a row in the field
of view of a 35 mm camera. The experiment was housed in a 9-inch-high, 19 by
21-inch (0.48 by 0.53 meter) rectangular metal container and was installed in
place of a middeck locker in the crew cabin.

Mesoscale Lightning
Experiment (MLE) was an experiment designed to obtain night time images of
lightning in an attempt to better understand the effects of lightning
discharges on each other, on nearby storm systems and on storm microbursts and
wind patterns and to determine interrelationships over an extremely large
geographical area.The experiment used Shuttle payload bay cameras to
observe lightning discharges at night from active storms. The experiment used
color video cameras and a 35mm hand-held film camera and provided synoptic
coverage of an area roughly 200 by 150 miles directly below the Shuttle.

One of the most important aspects of biotechnical and biomedical
technology involves separation processes. Cell types producing important
compounds must be separated from other cell types. Cells with important
biomedical characteristics must be isolated to study those characteristics.
This experiment involved a separation method termed two-phase
partitioning.The Phase Partitioning Experiment (PPE) was designed to
fine tune understanding of the role gravity and other physical forces play in
separating, i.e., partitioning biological substances between two unmixable
liquid phases.Most people are use to the two-phase systems formed by mixing
oil and water. In PPE, the systems are simple saline solutions containing two
different polymers. When the polymers are dissolved in solution, they separate.
On Earth this results in the lighter phase floating on top of the heavier one.
In space the demixed phases exhibit more complex behavior, looking somewhat
like an egg which has a yolk floating inside of the egg white.Phase
partitioning has been shown on Earth to yield more effective, large-scale cell
separations than any other method, differentiating cells on the basis of their
surface properties. Space experiments should improve efficiency of Earth-bound
partitioning and may allow scientists to carryout cell separations unobtainable
on Earth.The experiment was part of a category of handheld microgravity
experiments designed to study the effects of the low gravity of spaceflight on
selected physical processes.The experiment consisted of an 18-chambered
experimental module filled with small quantities of two-phase systems, each
differing in various physical parameters (e.g. viscosity). The module was
shaken to mix the phases and the separation of the phases was photographed
periodically by a mission specialist.A 15-chamber version of the PPE was
successfully flown on STS-51D, and the
experiment is being considered for at least two more flights.

Earth
Limb Radiance Experiment (ELRAD) was an experiment developed by the Barnes
Engineering Co., designed to photograph the Earth's "horizon twilight glow"
near sunrise and sunset.The experiment was expected to provide photographs
of the Earth's horizon that will allow scientists to measure the radiance of
the twilight sky as a function of the sun's position below the horizon. This
information should allow designers to develop better, more accurate horizon
sensors for geosynchronous communications satellites.Communications
satellites routinely use the Earth's horizon or "limb" as a reference for
attitude control. Barnes Engineering was developing an advanced horizon sensor
that uses visible light to sense the Earth's limb. Near the spring and fall
equinoxes, however, the Earth eclipses the sun once a day (as seen from the
satellites' orbit), often for as long as 70 minutes.During these eclipses,
the Earth's horizon is invisible to a visible light horizon sensor. However,
the Earth's upper atmosphere scatters sunlight to produce a thin ring of blue
and ultraviolet light that would still be visible even during an eclipse. This
ring of light is what ELRAD photographed.ELRAD consisted of a 35mm Nikon
camera, an 85mm lens, a blue lens filter and a timing device known as a
intervalometer. Astronauts onboard the Space Shuttle mounted ELRAD in one of
the Shuttle's windows and pointed it toward the Earth's horizon. The
intervalometer was set to take one photograph every 10 seconds. Three sequences
of photographs were taken, one just before sunrise and two just after sunset.
After the mission, the exposed film was developed by
NASA and provided to Barnes Engineering, along with a
sensitivity curve. Barnes Engineering then computed the radiance of the
scattered light as recorded on the film.

Special instrumentation to
record the environment experienced by Discovery during the
STS-26 mission was aboard the orbiter mounted in the
payload bay.The Orbiter Experiments Autonomous Supporting
Instrumentation System (OASIS) was designed to collect and record a variety
of environmental measurements during various in-flight phases of the orbiter.
The primary device was a large tape recorder which is mounted on the aft, port
side of the orbiter. The OASIS recorder could be commanded from the ground to
store information at a low, medium or high data rate.The information was
used to study the effects on the orbiter of temperature, pressure, vibration,
sound, acceleration, stress and strain. It also will be used to assist in the
design of future payloads and upper stages.The OASIS data were collected
from 101 sensors mounted on three primary elements. The sensors were located
along the sills on either side of the payload bay, on the airborne support
equipment of the Inertial Upper Stage and on the tape recorder itself. These
sensors were connected to accelerometers, strain gauges, microphones, pressure
gauges and various thermal devices on the orbiter.

The orbiter sustained
only minor Thermal Protection System tile damage, and the redesigned
post-Challenger solid rocket boosters showed no signs of leakage or overheating
at any of the joints.

Two minor problems occurred during the flight.
After ascent, the Flash Evaporator System for cooling the orbiter iced up and
shut down, increasing the crew cabin temperature to approximately 87 °F (31
°C). The problem was resolved on Flight Day 4 and cooler temperatures
resulted. A Ku-band antenna for communications was deployed on Flight Day 2,
but it failed to respond properly and had to be stowed for the remainder of the
mission.